Gibberellic Acid Inhibits Floral Formation and Delays Flower Differentiation in '0900 Ziraat' Sweet Cherry Cultivar

This paper reports on the effects of gibberellic acid (GA3) on floral formation and the potential for GA3 to reduce flower primordia formation in sweet cherry (Prunus avium L.). GA3 was applied to 4-year-old '0900 Ziraat'/'Gisela 5' trees at two growth stages (early flowering and beginning of fruit development) at the doses of 0, 25, 50, 100, and 250 mg L-1, for a 2-year period. Bud samples were taken from the beginning of July to the end of September in both years in six sequential dates. During the dormant seasons, buds were collected to determine number of flowers per bud. Samples were fixed and stored in a solution of formalin, 70% ethanol and glacial acetic acid (10:50:5, v/v). Flower formation in the buds was examined using a stereo zoom microscope and the morphological changes in each sample were recorded using a camera mounted on the microscope. Number of flowers per bud was negatively and linearly related to GA3 concentration. Floral formation in '0900 Ziraat' sweet cherry (untreated control) started in early-July and continued until mid-September. The progress during which the sepal, petal, stamen and pistil primordia were differentiated was considerably slower at GA3 applications. Imperfection of the floral buds was observed as the floral organs being replaced by leaf-like appendages or as none of the flower buds having one normally-developed flower primordia or as floral organs or flower primordia being much smaller than the other.